Automotive vehicle electrohydraulic braking (EHB) systems in which electrohydraulic actuators are controlled to drive brake pressure toward a desired pressure are known. Known EHB systems may provide closed-loop brake pressure control in individual braking channels of an automotive vehicle by periodically calculating brake pressure error as a difference between a desired or commanded brake pressure and sensed brake pressure, and applying the brake pressure error to a control function designed to efficiently drive the error toward zero.
Expensive fluid pressure transducers are typically used to sense brake pressure for closed-loop EHB control. The pressure sensed by such transducers may not correspond closely to actual braking pressure, due to the many mechanical losses that may occur between the point of brake pressure application and the position of the transducer. Additionally, such transducers may operate over a substantially limited pressure range or with unacceptably granular resolution. Pressure transducer reliability may be unacceptable for many EHB applications. Accordingly, it would be desirable to provide for closed-loop EHB without dependence on hydraulic pressure transducers.
The independent brake channel control of conventional EHB systems may result in uneven brake pressure application between the braking channels of the vehicle due, for example, to variations in brake pad wear, brake line length, and the amount of air in brake lines. Braking controllability and smoothness, effectiveness, and durability may be reduced due to such uneven brake pressure application. Accordingly, it would be desirable to provide for EHB control in which uneven braking pressure between individual EHB channels is minimized.